In recent years, CE (Consumer Electronics) apparatuses such as digital TV (digital televisions) and BD (Blu-ray Disc) recorders have various functions thanks to compatibility with network and the like. As a result, applications have been increasing which do not provide sufficiently comfortable operability in screen display apparatuses having operating devices such as conventional remote-control devices (remote control).
For instance, as an application used by a screen display apparatus, there is a web browser for browsing contents on the Internet. Furthermore, examples of such an application include a picture viewer for browsing, using a digital TV or a BD recorder, image data recorded on an SD (Secure Digital) card or the like. Moreover, the examples of the application include a keyboard application for inputting a search string when search or the like is performed with the web browser or the like.
There has been a growing need for new screen display apparatuses which are flexibly compatible with network-compatible applications to be newly developed in the future, in addition to such an application, and have a high operability.
For example, as an implementation of the new screen display apparatuses, there is a screen display apparatus which includes an operating device having a touchpad instead of a remote control having a conventional fixed hardware key. Such a screen display apparatus allows free pointing on a GUI (Graphical User Interface) displayed on a screen of a digital TV or the like. A cursor displayed on the GUI (a pointer indicating an operation position on the GUI) is designed to move in response to an operation of a user trailing a user's finger on the touchpad.
Consequently, the user can operate the GUI without looking at the user's hand, and thus can intuitively operate various applications without a complex operation and memorization of an arrangement of the hardware key of the screen display apparatus.
Among such new screen display apparatuses, there is a screen display apparatus including an operating device which is top-bottom and left-right symmetrical. The user can freely operate the screen display apparatus without concern for a direction to which the operating device is held (which side of the operating device the user recognizes as an anterior direction while holding the operating device) and a hand of the user with which the operating device is held (with which one of right hand and left hand the operating device is held). Even when the user holds the operating device in any direction, such a new screen display apparatus needs to properly control and display the cursor on the GUI in response to the operation of the user.
In the meantime, there are several techniques known as a technique of checking a direction of the operating device included in the conventional screen display apparatus. It is to be noted that when the operating device is physically integrated with the screen display apparatus, the direction of the operating device is the same as that of the screen display apparatus.
For instance, PTL 1 discloses, as the screen display apparatus, a mobile terminal which a user can operate with one hand.
The mobile terminal includes a state detecting unit which checks a state of the mobile terminal such as which part of the mobile terminal is held (also referred to as gripped) and which directions are upward and downward directions (upper and lower directions) of the mobile terminal. The state detecting unit checks the state of the mobile terminal, using a contact sensor (also referred to as a pressure sensor, gripping sensor, or touch sensor) and a gravity sensor (also referred to as an acceleration sensor) that are attached to the mobile terminal. The mobile terminal then determines a display direction of a screen using the state detection result of the state detecting unit.
In other words, the mobile terminal checks its direction based on the detection results of the contact sensor and the gravity sensor.                PTL 2 discloses, as the screen display apparatus, a mobile terminal apparatus which makes it possible to switch between display directions of a display unit in response to a button operation of a user or a state of holding the mobile terminal apparatus by the user. A pressure sensor which is provided to a peripheral part of the mobile terminal apparatus detects the state of holding the mobile terminal apparatus by the user. In other words, the mobile terminal apparatus checks its direction based on the clear instruction from the user or the detection result of the state of holding by the pressure sensor.        
PTL 3 discloses, as the screen display apparatus, an electronic paper device of which outer peripheral part includes touch sensors, and which makes it possible to optimize a display direction depending on a way a user holds the electronic paper device.
PTL 3 discloses a technique of checking the direction of the electronic paper device using the touch sensors, which is the same as the techniques disclosed by PTL 1 and PTL 2. However, PTL 3 indicates, as a problem in a method of checking, using only touch sensors, a direction of a device, a case where upper and lower directions of display may be reversed depending on a way the user holds the device. In this regard, PTL 3 discloses that increasing accuracy of estimating, using a gravity sensor jointly, the way the user holds the device enables correct display.